--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/+time/CdiffTimeDep.m	Thu Nov 15 16:36:21 2018 -0800
@@ -0,0 +1,55 @@
+classdef CdiffTimeDep < time.Timestepper
+    properties
+        D
+        E
+        S
+        k
+        t
+        v
+        v_prev
+        n
+    end
+
+
+    methods
+        % Solves u_tt = Du + E(t)u_t + S(t)
+        % D, E, S can either all be constants or all be function handles,
+        % They can also be omitted by setting them equal to the empty matrix.
+        % CdiffTimeDep(D, E, S, k, t0, n0, v, v_prev)
+        function obj = CdiffTimeDep(D, E, S, k, t0, n0, v, v_prev)
+            m = length(v);
+            default_arg('E', @(t)sparse(m,m));
+            default_arg('S', @(t)sparse(m,1));
+
+            obj.D = D;
+            obj.E = E;
+            obj.S = S;
+
+            obj.k = k;
+            obj.t = t0;
+            obj.n = n0;
+            obj.v = v;
+            obj.v_prev = v_prev;
+        end
+
+        function [v,t] = getV(obj)
+            v = obj.v;
+            t = obj.t;
+        end
+
+        function [vt,t] = getVt(obj)
+            vt = (obj.v-obj.v_prev)/obj.k; % Could be improved using u_tt = f(u))
+            t = obj.t;
+        end
+
+        function state = getState(obj)
+            state = struct('v', obj.v, 'v_prev', obj.v_prev, 't', obj.t, 'k', obj.k);
+        end
+
+        function obj = step(obj)
+            [obj.v, obj.v_prev] = time.cdiff.cdiff(obj.v, obj.v_prev, obj.k, obj.D, obj.E(obj.t), obj.S(obj.t));
+            obj.t = obj.t + obj.k;
+            obj.n = obj.n + 1;
+        end
+    end
+end
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